The theorem of Ionescu Tulcea and Marinescu, a generalization of the ergodi
c theorem of Doeblin and Fortet, is derived as a result of the deLeeuw-Glic
ksberg decomposition. This complements recent work of Sine which derives as
ymptotic periodicity results for constricted Markov operators from the deLe
euw-Glickstein decomposition. A weak form of the Ionescu Tulcea and Marines
cu theorem is obtained from the deLeeuw-Glickstein decomposition.